Danny weakens further; 94L worth watching

By: Dr. Jeff Masters , 1:54 PM GMT on August 28, 2009

Share this Blog
2
+

Tropical Storm Danny continues to weaken, and may merely be a tropical depression. Data from the Hurricane Hunters early this morning showed top winds of just 40 mph at the surface, and satellite intensity estimates of Danny's strength are now rating the storm a tropical depression. Danny looks very disorganized on satellite imagery (Figure 1), with the low-level circulation center exposed to view. There is no heavy thunderstorm activity near Danny's center, and only a small area of heavy thunderstorms lying several hundred miles east of the center.


Figure 1. Morning satellite image of Danny, showing the exposed swirl of clouds where Danny's center is, well displaced from the heaviest thunderstorm activity to the east.

The forecast for Danny
With wind shear at 15 knots this morning, and forecast to increase to 20 knots tonight and 30 knots Saturday morning, is is unlikely Danny will be able to strengthen to more than a 50 mph tropical storm. Dry air from the upper-level low that has been keeping Danny disorganized continues to be a problem for the storm, as well. The GFDL and HWRF models continue to insist Danny will strengthen to a strong tropical storm or weak Category 1 hurricane, but this seems very unrealistic given Danny's current struggles. With Danny's heavy thunderstorms all on the east side of the storm, it is unlikely that New England will feel tropical storm force winds from Danny when it scoots past on Saturday. Large swells from Danny creating high surf along the beaches of New England will be the primary hazard from the storm.

Massachusetts hurricane history
Two tropical storms have affected Massachusetts in the past decade, though neither of these storms brought sustained winds of tropical storm force (39 mph) to the state. Tropical Storm Beryl of 2006 just missed Cape Cod as a weak tropical storm with 45 mph winds. Beryl brought wind gusts to tropical storm force to Nantucket Island, and a 1 foot storm surge. Tropical Storm Hermine hit southeast Massachusetts on August 31, 2004, as a minimum-strength tropical storm with 40 mph winds. No land stations in Massachusetts reported tropical storm force winds during Beryl. The last time Massachusetts measured tropical storm force winds was in 1991 during Hurricane Bob, which hit Rhode Island as a Category 2 hurricane. Provincetown, Massachusetts measured sustained winds of 98 mph, gusting to 115 mph, and Buzzard's Bay received a 15 foot storm surge.


Figure 2. Tropical wave 94L, a few hundred miles west of the Cape Verdes Islands.

Invest 94L
A well-organized tropical wave (94L) lies a few hundred miles west-southwest of the Cape Verdes Islands. This disturbance has shown little change this morning. This morning's QuikSCAT pass shows a complete circulation, elongated in the east-west direction, with top winds of 30 mph. Satellite imagery shows only a small amount of heavy thunderstorm activity near the circulation center, but considerable thunderstorm activity south of the center. Shear is low, about 10 knots, and is expected to remain low to moderate, 5 - 15 knots, over the next five days. The waters are warm enough to support development, 28°C, and are expected to remain in the 27 - 28°C range over the next five days. The dry Saharan Air Layer (SAL) lies about 200 miles to the north and west of 94L, and it appears from water vapor satellite imagery that a modest amount of dry air from the SAL is now being ingested into the storm, slowing development. Dry air will continue to slow development until 94L's heavy thunderstorm activity can moisten the atmosphere enough to shield the storm from the Saharan Air Layer. NHC is giving 94L a medium (30 - 50% chance) of developing into a tropical depression by Sunday. The GFDL and SHIPS models both predict 94L will be a Category 1 hurricane five days from now. However, the HWRF model does not develop 94L. Most of the models predict 94L will take a significant northward jog 3 - 5 days from now, in response to a strong trough of low pressure passing to the north (this is the same trough of low pressure that will be recurving Danny out to sea). It is then probable that 94L will be forced to the west again as the high pressure ridge steering the storm builds back in, and 94L will likely be a few hundred miles northeast of the Northern Lesser Antilles Islands seven days from now.

I'll have an update this afternoon.

Jeff Masters

Reader Comments

Comments will take a few seconds to appear.

Post Your Comments

Please sign in to post comments.

or Join

Not only will you be able to leave comments on this blog, but you'll also have the ability to upload and share your photos in our Wunder Photos section.

Display: 0, 50, 100, 200 Sort: Newest First - Order Posted

Viewing: 124 - 74

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12Blog Index

Quoting Chicklit:
Hi Charleston. Both images are the same, from 13:15 UTC.
It's now 14:55 UTC. TimeClock
also 10:55 a.m. EST.
That Quickscat would've been from 8 a.m. this morning.
Good morning : )
Member Since: Posts: Comments:
Quoting P451:


They barely pick up on it. The CMC does. The GFS sorta. The NGPs not at all. So it wasn't worth putting together.

Again, models just don't do well until they have an established system with several runs under their belts.

Given the easterly shear keeping the center a few degrees east of the large area of convection it will still be some time before 94L gets organized. I would be surprised to see a red shading at 2pm. It hasn't changed much. Convection at 36-40W and the Low is around 33W.



So? Danny was always like that yet it was named.
Member Since: Posts: Comments:
Nott gettng this: Most of the 8am (EST)GFS ensemble points 94L to the carribean but the GFS 8am run is ponting well awa to the North - shouldn't it be an average of all the ensembles...

or am I missing something here...!!
Quoting 786:
models don't seem to have a good handle on this, they show a system moving WNW at a slow forward speed and 94L continues much faster at a low latitude - its been off the tracks of the model guidance.

Hi 786. Yes. Fast forward doesn't allow it to gain full signature. Slow it down and it will appear much better organized.
Member Since: Posts: Comments:
Member Since: July 3, 2005 Posts: 426 Comments: 128871
haha i think you got it backwards my friend. as soon as your qb steps back our d will be all over him. can you say 10 sacks. haha
Member Since: Posts: Comments:
Quoting NEwxguy:
I don't think Danny has ever been a true TS,its seems like his convection has always been to the northeast and east.


A ts just means a low level low pressure with 35mph winds, so it fits the criteria. 90L in late may fit too, in fact was a lot more organized than danny, but they refused to name it.
Member Since: Posts: Comments:
looking at the RGB sat loop it appears that 94L is near 9.5N 36.2W mowing slight south of due west
Member Since: Posts: Comments:
116. 786
models don't seem to have a good handle on this, they show a system moving WNW at a slow forward speed and 94L continues much faster at a low latitude - its been off the tracks of the model guidance.
Member Since: Posts: Comments:
Member Since: July 3, 2005 Posts: 426 Comments: 128871
Hi Charleston. Both images are the same, from 13:15 UTC.
It's now 14:55 UTC. TimeClock
also 10:55 a.m. EST.
That Quickscat would've been from 8 a.m. this morning.
Member Since: Posts: Comments:
interesting show about hurricane katrina on the discovery channel
Member Since: Posts: Comments:
Quoting tornadodude:


ha my grandma generates bigger swells than that when she gets in the bath tub....


oh no you di-int!
Member Since: Posts: Comments:
Quoting StormW:
Morning aggie!

Howdy! Y'all take care...got things to do.
Member Since: Posts: Comments:
I don't think Danny has ever been a true TS,its seems like his convection has always been to the northeast and east.
Member Since: September 6, 2007 Posts: 883 Comments: 15862
Quoting P451:
00Z CMC



06Z GFS



00Z NGP (model shifts from 6hr to 12hr frames - thats not a sudden acceleration)





what do the models say for 94? I think it should at least be red, if not a TD. Just some dry air going into it, like danny. The atlantic is so @#*# dry this year, its crazy.
Member Since: Posts: Comments:
Quoting BrockBerlin:
I still think Ana was a worse system than Danny, at least Danny had decent winds at some points.

I agree, TS Ana went through several periods of "on/off again convection", but TS Danny has just been in an fairly unfavorable environment, despite SST of 84-86! The old ULL, wind shear, dry slot, and trough to the west kept is totally discombobulated!!
Member Since: Posts: Comments:
Quoting Chicklit:
13:45 UTC it is now 14:50 UTC, so this was 94L an hour ago:

This one was at 13:15 UTC (hour and a half ago ~9:15 a.m.):

Last time I checked, low shear, low SAL and moving into SST's about 29.
How fast is it moving?
Not sure... this is the RAMMB about a little shy of 5 hours ago. Member Since: Posts: Comments:
i just dont have a good feeling bout 94l at all for us in fl the way that high builds back could cause stairstepping. jmo no wishcasting cause i dont want the game to be postponed
Member Since: Posts: Comments:
Quoting BrockBerlin:
I still think Ana was a worse system than Danny, at least Danny had decent winds at some points.

What is the deal with your handle, anyway? Did you have to pick that?
Member Since: Posts: Comments:
96. 786
Aug 28, 2009 1200 10.5N 36W 29.86 (1011) 29(25)
Aug 28, 2009 0600 10.3N 33.4W 29.8 (1009) 2(25)
Aug 28, 2009 0000 10.2N 30.8W 29.8 (1009) 2(25)
Aug 27, 2009 1800 10.2N 28.8W 29.8 (1009) 2(25)
Aug 27, 2009 1200 10.3N 26.3W 29.8 (1009) 2(25)
Aug 27, 2009 0600 10.7N 24.1W 29.8 (1009) 2(20)
Aug 27, 2009 0000 10.9N 22.6W 29.8 (1009) 2(25)
Aug 26, 2009 1800 11.1N 21W 29.8 (1009) 23 (20)
Aug 26, 2009 1200 11.4N 19.5W 29.8 (1009) 23(20)

94L moving just N of W, either it is moving quite quickly or there has been a center relocation further West, at 2 AM it was 450 miles from Cape Verde and at 8 AM it was 850 miles away. Pressure has increased sinced this morning. If it continues this way then it may miss the trough, if there is a recurve I think it may follow Bill. Two scenerios Bill or Caribbean - this has been the year of the recurve although the high is forecast to build in.
Member Since: Posts: Comments:
Quoting BrockBerlin:
I thought the CHIPS model usually went to ridiculous intensities with storms, I believe it made BIll a 165 knot hurricane.

It did at least have an ensemble member that did that...
Not saying it is perfect, but I'll gladly take baby step in forecast intensity improvements.

L8R, y'all.
Member Since: Posts: Comments:
13:15 UTC it is now 14:50 UTC, so this was 94L an hour and a half or so ago:

Funktop 13:15 UTC

Last time I checked, low shear, low SAL and moving into SST's about 29.
How fast is it moving?
Member Since: Posts: Comments:
Member Since: Posts: Comments:
Link

Turn on lat/lon and trop pts. Danny tracking pretty far west of forecast...
Member Since: Posts: Comments:
Quoting NickThompson:
Does anybody know what maintains a circulation in the absence of convection?



momentum.
Member Since: Posts: Comments:
87. IKE
TROPICAL STORM DANNY DISCUSSION NUMBER 9
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL052009
1100 AM EDT FRI AUG 28 2009

THE CENTER OF DANNY REMAINS EXPOSED THIS MORNING...AND OVER THE PAST
COUPLE OF HOURS HAS BEEN MOVING ALMOST DUE WESTWARD AWAY FROM THE
DEEP CONVECTION. NOAA BUOY 41047 WELL SOUTHEAST OF THE CENTER
REPORTED A 1-MINUTE PEAK SUSTAINED WIND OF 31 KT AT 1100 UTC. THE
INITIAL INTENSITY IS HELD AT 35 KT...ASSUMING THAT HIGHER WINDS
STILL EXIST WELL EAST OF THE CENTER. AN AIR FORCE RESERVE HURRICANE
HUNTER AIRCRAFT WILL BE INVESTIGATING DANNY LATER THIS AFTERNOON TO
PROVIDE MORE INFORMATION ON ITS INTENSITY AND STRUCTURE.

THE INITIAL MOTION ESTIMATE IS 325/9...A COMPROMISE BETWEEN THE
SHORT TERM WESTWARD MOTION AND THE LONGER TERM NORTH-NORTHWESTWARD
MOTION OBSERVED OVERNIGHT. THE FORECAST IS ADJUSTED TOWARD THE WEST
DUE TO THE INITIAL MOTION AND ACTUALLY LIES WEST OF ALL THE
DYNAMICAL MODELS AT 12 HOURS...AS THESE MODELS IMMEDIATELY TURN
DANNY NORTHWARD. LATER IN THE FORECAST PERIOD...THE TRACK IS
VERY CLOSE TO THE TVCN MULTI-MODEL CONSENSUS. BY 36 HOURS...THIS
POSITION IS JUST SOUTH OF THE COAST OF MASSACHUSETTS...WITH THE
GFS...ECMWF...AND GFS ENSEMBLE MEAN SIGNIFICANTLY LEFT OF THE
CONSENSUS...AND MOST OF THE OTHER GUIDANCE CLUSTERED TO THE RIGHT.
BEYOND THAT TIME...DANNY SHOULD BE ACCELERATING TOWARD THE
NORTHEAST THROUGH THE CANADIAN MARITIMES AND EAST-NORTHEASTWARD
INTO THE NORTH ATLANTIC.

IT SHOULD BE NOTED THAT THERE ARE A COUPLE OF ALTERNATIVE SCENARIOS
THAT COULD OCCUR. THE SHALLOW BAM MODEL REPRESENTS AN EVEN MORE
WESTWARD TRACK THAT COULD OCCUR IF DANNY LOSES ALL OF ITS DEEP
CONVECTION. IT IS ALSO POSSIBLE THAT A NEW CENTER COULD RE-FORM
UNDER THE DEEP CONVECTION FARTHER EAST. EITHER OF THESE SCENARIOS
WOULD LIKELY REDUCE THE THREAT TO THE U.S. EAST COAST.

THE INTENSITY FORECAST SHOWS THE POSSIBILITY FOR A LITTLE
STRENGTHENING IN THE NEXT 12 HOURS...BUT AFTER THAT TIME THE
CYCLONE WILL BE MOVING INTO A VERY UNFAVORABLE ENVIRONMENT...WITH
THE SHIPS MODEL SHOWING WIND SHEAR INCREASING TO OVER 30 KT BY 24
HOURS AS DANNY INTERACTS WITH A DEEP-LAYER TROUGH OVER THE EASTERN
UNITED STATES. THE GLOBAL MODELS AND PHASE SPACE DIAGRAMS SHOW THAT
DANNY WILL BEGIN EXTRATROPICAL TRANSITION BEGINNING BY 48
HOURS...AND THAT THE CYCLONE WILL BE FULLY EXTRATROPICAL BY 72
HOURS. THIS EVOLUTION IS REFLECTED IN THE OFFICIAL FORECAST...WHICH
SHOWS AN EXPANDING WIND FIELD AS DANNY MOVES FROM THE CANADIAN
MARITIMES INTO THE NORTH ATLANTIC.

DESPITE THE WESTWARD SHIFT IN THE TRACK...A TROPICAL STORM WARNING
WILL NOT BE ISSUED FOR THE COAST OF NORTH CAROLINA AT THIS
TIME...DUE TO THE CURRENT AND EXPECTED LIMITED EXTENT OF TROPICAL
STORM FORCE WINDS ON THE WEST SIDE OF THE CIRCULATION. THE TROPICAL
STORM WATCH REMAINS IN EFFECT IN CASE THE WIND FIELD BECOMES BETTER
DEFINED ON THE WESTERN SIDE OF DANNY OR IF THE FORECAST CONTINUES
TO SHIFT WESTWARD. A TROPICAL STORM WATCH MAY ALSO BE NEEDED FOR
PORTIONS OF THE COAST OF NEW ENGLAND LATER TODAY.

FORECAST POSITIONS AND MAX WINDS

INITIAL 28/1500Z 30.1N 75.5W 35 KT
12HR VT 29/0000Z 32.5N 75.7W 40 KT
24HR VT 29/1200Z 36.2N 74.1W 40 KT
36HR VT 30/0000Z 40.7N 70.7W 40 KT
48HR VT 30/1200Z 44.6N 65.1W 40 KT...INLAND
72HR VT 31/1200Z 49.6N 52.5W 40 KT...EXTRATROPICAL
96HR VT 01/1200Z 52.5N 38.0W 40 KT...EXTRATROPICAL
120HR VT 02/1200Z 54.5N 21.5W 45 KT...EXTRATROPICAL

$$
FORECASTER BRENNAN

Member Since: Posts: Comments:
I believe TS Danny should win an award for the squirreliest tropical system of 2009! PLEASE remember, even LIL TS Danny can cause dangerous SURF!! But 94L looks good, wonder if the ULL in the S Central Atlantic will have any effect on its development and direction?
Member Since: Posts: Comments:
Quoting nrtiwlnvragn:


There is currently an upgrade to HWRF waiting in the que that includes a modification to the initialization that testing has shown to improve intensity forecasts. Its been waiting for the switchover to the new computers, now changes to SREF and GEFS are ahead of it in the que.

I sincerely hope it is a huge improvement.
Honestly, as a NWP-type met, I find it a little embarrassing for our entire community that a model developed decades after some of the others performs so badly. In it's current state, are we better off in having it as a guidance tool than we were before it was built? I don't think so.
Member Since: Posts: Comments:
From 8am to 11am, Danny's movement was 270 at 5mph.

Stuck!
Member Since: May 27, 2008 Posts: 0 Comments: 461
Several hundred mile Noth East of the islands? I just don't see it...
Quoting IKE:


Poor bathtub. OMG.


haha yeah, obviously i was kidding, but its nice to "lighten" the mood every now and then
Member Since: Posts: Comments:
Quoting IKE:
LARGE SWELLS FROM DANNY ARE EXPECTED TO PRODUCE DANGEROUS SURF
CONDITIONS AND LIFE-THREATENING RIP CURRENTS ALONG THE U.S. EAST
COAST DURING THE NEXT DAY OR TWO.
...

from a 40 mph tropical storm?


well, there have been "life-threatening" rip currents off the US east coast all summer...actually know of someone from KC who died off the SC coast in July.
Member Since: Posts: Comments:
both look bad at this point in time ... esp danny
Member Since: Posts: Comments:
78. IKE
Quoting tornadodude:


ha my grandma generates bigger swells than that when she gets in the bath tub....


Poor bathtub. OMG.
Member Since: Posts: Comments:


windfield has expanded
Member Since: Posts: Comments:
Quoting IKE:
LARGE SWELLS FROM DANNY ARE EXPECTED TO PRODUCE DANGEROUS SURF
CONDITIONS AND LIFE-THREATENING RIP CURRENTS ALONG THE U.S. EAST
COAST DURING THE NEXT DAY OR TWO.
...

from a 40 mph tropical storm?


Most likely due to the system being stalled for so long. That whole "long fetch" thing.
Member Since: May 27, 2008 Posts: 0 Comments: 461
Quoting fmbill:


Ah...yes, I see your point. But mostly, I was making an observation on the Danny's movement (or lack thereof). Faye got "stuck over florida and dumped a bunch of rain.

I wonder what the total rainfall under that Danny's area of thunderstorms is. You could probably measure it in feet!
Good point.
Member Since: Posts: Comments:
Quoting IKE:
LARGE SWELLS FROM DANNY ARE EXPECTED TO PRODUCE DANGEROUS SURF
CONDITIONS AND LIFE-THREATENING RIP CURRENTS ALONG THE U.S. EAST
COAST DURING THE NEXT DAY OR TWO.
...

from a 40 mph tropical storm?


ha my grandma generates bigger swells than that when she gets in the bath tub....
Member Since: Posts: Comments:

Viewing: 124 - 74

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12Blog Index

Top of Page

About

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.

Local Weather

Mostly Cloudy
51 °F
Mostly Cloudy